# Quick Answer: Floor Joist Are What Size In Residential Construction?

## What size should floor joists be?

A. Carl Hagstrom responds: The rule of thumb that I like to use when sizing uniformly loaded residential floor joists is “half the span plus two.” First, round the clear span of the floor joist up to the nearest foot, and divide by two. Then add two to the answer.

## Can I use 4×2 for floor joists?

4×2 timber floor joists on the ground floor have been used for decades but should be no more than 16 inch or 400 mm centres and be supported at no more than 2 metre centres, 6ft or 1.8 m is preferable and practical.

## What size wood is used for floor joists?

Lumber graded as #2 is the most common choice for floor joists and other framing lumber. It has more knots and defects than higher grades, but usually not enough to cause significant loss of bending strength.

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## What is code for floor joist?

Floor Joist Building Code Requirements

The joist must have a minimum of 1 1/2″ riding on the wall or beam. If the joists are lapped, then they must be lapped at least 3″. Maximum end notches for 2 x 8, 2 x 10, and 2 x 12 respectively are 1 13/16″, 2 5/16″, and 2 13/16″.

## Are 2×6 OK for floor joists?

How do I keep them even? In general terms, joists spaced 16 inches on center can span 1.5 times in feet their depth in inches. A 2×8 up to 12 feet; 2×10 to 15 feet and 2×12 to 18 feet. 2×6 joists should only be used on ground-level decks that do not require, and will not provide for, any guards.

## How far can a 2×6 floor joist span without support?

How far can a 2×6 Rafter span without support? The table states that 2 X 6 rafters spaced 16 inches on center (o.c) can span a maximum distance of 13 feet 5 inches.

## What is the maximum span of a 2×6 floor joist?

Max. Live Load 30 lbs/ft2 (1436 N/m2)

Maximum Span (ft – in)
Nominal Size (inches) Joist Spacing Center to Center (inches) Lumber Grade
2 x 6 12 12′ – 6′”
16 11′ – 4″
24 9′ – 11″

## Do I need noggins in floor joists?

If the span of your joists is less than 2.5m then you don’t need to include any noggins. Up to 4.5m span one row of noggins at mid span is needed. Above 4.5m span use two rows of noggins at third points. Noggins need to be at least 38mm wide and the depth should be at least 0.75 times depth of joists.

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## How do you calculate floor joists?

The basic math is to divide the width by the on center spacing, round up to the nearest integer and then add one for the first joist (at the zero position). The length is used for the length of the joists or I-joists.

## What size beam do I need for a 20 span?

you looking around 4×14, 4x 16 for a 20span. i would use a glue lam and not a solid beam ( 1 pc ). steel would be best for strength and space.

## Which is stronger 6×6 or 3 2×6?

Beam bending strength is proportional to the width of the beam, but to the cube of the height. Fanman, it may be counter-intuitive, but engineering tables indicate that a three-layer 2×6 will bend less (have greater strength) than a one piece 6×6 timber, even with the lesser actual width of the surfaced 2x material..

## Should I use treated lumber for floor joists?

Generally, building codes require pressure-treated or naturally durable wood for the following applications: Joists or the bottom of structural floors without joists that are within 18″ of exposed soil. Beams or girders closer than 12″ to exposed soil.

## How far can a 2×10 beam span without support?

In general terms, joists spaced 16 inches on center can span 1.5 times in feet their depth in inches. A 2×8 up to 12 feet; 2×10 to 15 feet and 2×12 to 18 feet.

## What is the depth of a floor joist?

The bulk of the floor’s thickness comes from the joists, which are the horizontal beams that carry the floor’s weight. Joists in home construction are usually made with 2-by-10 or 2-by-12 lumber, which are 9 1/4 and 11 1/4 inches deep, respectively.